Consider the following set of processes on a single CPU machine, under an FCFS scheduling policy. Note that in the beginning only A exists; B is forked by A. Assume that the semaphores S1 and S2 have an initial value of 0.

Trace the execution of this set of processes. You need to clearly indicate when a process blocks and wakes up. In FCFS, a process will always keep execution until it is blocked.

Process A: A1; fork(B); wait(S1); A2; signal(S2);

Process B: B1; signal(S1); wait(S2); B2;

Note that A1, A2, B1, B2 are code segments in the process A or B. The trace can be in the form of "Process:Segment; Process:Segment.... ". Example of trace format: A: A1; B: B1; B:signal(S1). (This is not the answer of course.)